Field of Invention
The present invention relates to a method for accurately testing yarn hairiness through stretching one-directionally, which belongs to a technical field of textile testing.
Description of Related Arts
Hairiness is one of the important indexes of the yarn quality. Yarn hairiness is the fiber tail or the fiber loop exposed on the surface of the staple yarn. When the yarn is under a stress, the hairiness lacks holding points for resisting the tensile force and thus the hairiness is unhelpful to the yarn strength. When the yarn has excessive hairs, the friction force of the yarn increases and the yarn is liable to be broken in the subsequent process, which affects the processing efficiency. During the weaving process, the excessive hairs lead to the intertwined yarn and the unclear opening of the warping yarns, lowering the weaving efficiency and the weaving quality. The yarn hairiness further affects the appearance quality of the finished product. Thus, an accurate and fast testing of the yarn hairiness is the basic requirement in the textile enterprise.
The conventional methods for testing the yarn hairiness comprise the visual observation method, the weighing method and the photoelectric method. The visual observation method is to observe the yarn hairiness with the naked eyes after being magnified by the microscope. The weighing method comprises steps of: weighing the yarn, before and after cutting or burning off the hairiness; and then obtaining the weight ratio of the hairiness. The visual observation method and the weighing method are accurate and reliable. However, the visual observation method and the weighing method cost too much time, have a low efficiency and are unable to satisfy the requirement of the large-scale rapid test of the factory. The photoelectric method comprises steps of: converting the optical signal generated by the hairiness into the electric signal; and testing the yarn hairiness rapidly. The main commercial testers for the photoelectric method comprise: Uster hairiness tester, Switzerland; G566 hairiness tester of Zweigle, Germany; SDL098/98 hairiness tester of Shieley, England; and YG172A yarn hairiness tester of Changling, China. The US patent U.S. Pat. No. 4,948,260, Method and apparatus for examining hairiness of yarn, published on Aug. 14, 1990, disclosed the Uster hairiness tester for testing the yarn hairiness through a diffuse reflection. The testing principles of the Uster hairiness tester are described as follows. A continuous monochromatic light source (laser) is shined on the prominent hairiness of the yarn body; the hairiness scatters the parallel light; the yarn body is non-transparent and dark-colored, and the prominent hairiness of the yarn body leads to a bright-colored scatted light which is detected by the optical sensor; and the hairiness value H is tested, wherein the hairiness value H is the ratio of the total length to the testing length of the hairiness, without any unit. The testing method of the G566 hairiness tester comprises a step of: counting the amount of the yarn hairs for different lengths, through twelve corresponding photosensitive diodes which are arranged at different intervals. However, the G566 hairiness tester is merely able to count the hair amount of a single side of the yarn and has a large testing deviation. Thus, the G566 hairiness tester is not common in the enterprises. The SDL098/98 hairiness tester examines the yarn hairiness through the projection counting method. The projection counting method comprises steps of: adjusting the photoelectric detecting element to the appropriate position distant from the yarn according to the pre-set testing length of the hairiness, wherein the photoelectric detecting element is the photosensitive element; passing the testing point by the yarn at a constant speed; generating a luminous flux variation, due to sweeping over the photosensitive element by the prominent hairiness which is longer than the pre-set testing length; converting the luminous flux variation into the electric signal and then generating a counting pulse; and, obtaining the hairiness index of the pre-set testing hair length, wherein the hairiness index is the total amount of the counting pulses within the pre-set testing length of the yarn. The SDL098/98 hairiness tester has the similar technical principles with the YG172A hairiness tester of China. Both the SDL098/98 hairiness tester and the YG172A hairiness tester adopt the projection counting method.
Currently, the textile enterprises mainly adopt the Uster hairiness tester and the YG172A hairiness tester. The Uster hairiness tester has following advantages of: a fast testing speed, up to 400 m/min; a large sample testing amount; an automatic test; stable testing data and a high reproducibility; no interference caused by the dirt, the yarn guiding method and the testing speed during the test. However, the Uster hairiness tester has fatal defects. The fiber colors and the spatial electromagnetic waves affect the testing results; particularly, the Uster hairiness test is unable to reflect the yarn hair amount and the hairiness distribution, and has very limited information for describing the yarn hairiness. In accordance to the fatal defects of the Uster hairiness tester, the YG172A hairiness tester is able to test the index of the yarn hairs with different lengths ranging from 1 mm to 9 mm. The YG172A hairiness tester is able to intuitionally reflect the distribution of the various yarn hairs, without being affected by the fiber colors and the spatial electromagnetic waves. Unfortunately, it is well known that the hairiness surrounds the yarn; and, the YG172A hairiness tester, through the projection counting method, merely tests the hair amount of the single side of the yarn. Particularly, when the yarn runs at a certain running speed, the running speed induces the lodging of the yarn hairiness, leading to an inaccurate testing result, a poor repeatability and a low testing speed (generally 30 m/min).
With regard to the problem that the projection counting method merely tests the hair amount of the single side of the yarn, the article titled A new hairiness tester, cross section projection type, written by Hiramatsu T., Shimizu T. and Kinoshita K., published on Journal of The Textile Machinery Society of Japan, 22(4): 108-109 (1976), disclosed a method for testing the amount of the hairiness surrounding the yarn through projecting the cross section of the yarn. However, the method has an inconvenient operation and a poor visibility, and is unable to radically improve the testing result of the yarn hairiness. The main reason lies in the key technical problems of the lodging and the bending of the hairiness on the yarn surface during running the yarn dynamically, which remain unsolved. With regard to the above key technical problems, the Chinese patent publication CN101576503A, Electrostatic yarn hairiness tester, published on Nov. 11, 2009, disclosed that: the yarn entering the testing area is applied with the high-voltage static, which induces the mutual rejection and separation among the different yarn hairiness and between the hairiness and the yarn body, thereby stretching the hairiness straight; and, the electric machine is provided parallel with the yarn for attracting the hairiness, in such a manner that the yarn hairiness is almost vertical to the yarn body. According to the experiments, the electrostatic yarn hairiness tester has a good effect for the static yarn within a short time, but fails to vertically stretch the hairiness on the surface of the yarn which runs at a high speed. Particularly, because the yarn hairiness stretches along the different radial directions of the yarn body and stretches vertically to the yarn body, the hairiness of the different radial directions is unable to be all accurately projected to the projection receiver of the testing head at an equal length (i. e., the hair projection cannot be accurately equal to the hair true configuration for the most yarn hairs). Moreover, the high-voltage static causes the potential safety risk. The fiber static seriously attenuates to reduce the radial hair-stretching force in the air with certain humidity. Therefore, the electrostatic yarn hairiness tester fails in the industrial application. With regard to the key technical problems of the lodging and the bending of the hairiness on the yarn surface during running the yarn dynamically, the Chinese patent publication CN101671946A, Device for testing hairiness state of yarn under high-speed airflow, published on Mar. 17, 2010, disclosed a hairiness testing device which releases the high-pressure airflow to the hairiness surrounding the yarn which runs at the high speed, through the annular airflow channel. According to the aerodynamics, the flowing speed is different due to the different distances from the annular airflow outlet; the hairiness of different lengths has different air resistances. Thus, through the hairiness testing device, the hairiness on the surface of the yarn which runs at the high speed fails to fully stretch to be vertical to the yarn body. Similar to the electrostatic yarn hairiness tester, the hairiness testing device has the hairiness stretching in the different radial directions of the yarn body and vertically to the yarn body. The hairiness of the different radial directions is still unable to project the entire hairs' true configurations accurately on the projection receiver of the testing head for an accurately testing. Thus, the above methods and the devices all fail to solve the problem that the projection counting method is unable to rapidly, effectively, accurately and stably test the yarn hairiness.